1. Field of the Invention
This invention relates to processing of semiconductors used to make microelectronic devices and in particular to vacuum valves used in devices for processing such semiconductors.
2. Description of Related Art
Processing chambers are utilized for a variety of processes performed on microelectronic devices such as microelectronic circuits formed on silicon semiconductor substrates. Since these processes may be operated and performed under vacuum, vacuum gate valves are typically employed. Such vacuum gate valves, when used as wafer pass-throughs between vacuum chambers, are often referred to as slit valves. When the slit valve gate is open, semiconductor wafers may be moved from a transfer chamber to a load lock or process chamber or vice-versa. When closed, these valves prevent gas leakage between the transfer chamber and the process chamber. While such slit valves provide generally reliable seals for most processes, certain new deposition and clean processes have been found to rapidly attack elastomeric seal materials utilized in the slit valves. The attack on such elastomeric seal materials typically causes particle contamination or “adders” on wafers and also may cause vacuum leakage across the valve itself. Although a wide variety of elastomers are available, none thus far tested have shown a significant improvement in life over the normally employed fluoroelastomers.
The concept of purging the general area with an inert gas has been discussed in Japanese Patent Publication No. 6-185672. In this publication entitled Gate Valve Device For Use With A Vacuum, a guillotine type valve assembly employs gas ducts either in the valve seat or in the valve plate. These gas ducts are used to carry a non-active gas into the gap area between the valve plate and the valve seat. While such an approach has its advantages for shielding the O-rings used in the assembly with an inert gas during processing, the disclosed structure does not provide particularly effective control over the inert gas flow rate or distribution, and an overflow of such inert gas may interfere with the processing of the microelectronic device itself in the chamber.
Accordingly, there is a need for a valve system which may utilize a purge gas more efficiently and in a manner which would not tend to interfere with the processing of the microelectronic device.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide an efficient purge gas system for elastomeric seals in gate or slit valve assemblies used in microelectronic device processing.
It is another object of the present invention to provide a method and system whereby the purge gas is employed more efficiently.
It is a further object of the present invention to provide a method and system in which the purge gas is less likely to interfere with the processing of the microelectronic device in the processing chamber.